A printer which prints information such as a desired character or image on a sheet-like printing medium such as a paper sheet or film is widely used as an information output apparatus for a wordprocessor, personal computer, facsimile apparatus, and the like.
Various methods are known as printing methods for the printer. Especially an inkjet method has recently received a great deal of attention because this method can realize non-contact printing on a printing medium such as a paper sheet, easily prints in color, and is quiet. Because of low cost and easy downsizing, a popular inkjet arrangement is a serial printing system in which a printhead for discharging ink in accordance with desired printing information is mounted and prints while reciprocally scanning in a direction crossing the conveyance direction of a printing medium such as a paper sheet.
Recently, inkjet printers capable of so-called “marginless printing” (also referred to as “borderless printing” or “full-page printing”) are increasing in which printing is done on the entire surface of a printing medium (printing is done without any margin at the edge of a printing medium).
To realize marginless printing, printing data having a printing region larger than a printing medium used for printing is generated, and ink at a portion protruding from the printing medium is discharged onto a platen or an ink absorber arranged below (e.g., U.S. AA2003 035021 or EP A1 1285767 both of which correspond to Japanese Patent Laid-Open No. 2003-127341).
In order to shorten the data transfer time from the host apparatus and increase the printing speed in this type of printing apparatus, image data of each raster block including a plurality of rasters is generated by a printer driver installed in a host apparatus, and transferred to the printing apparatus. The printing apparatus rasterizes the received image data of each raster block in a buffer to convert the data into printing data (e.g., EP A3 959404, which corresponds to Japanese Patent Laid-Open No. 2000-099295).
However, the following problem is caused by marginless printing executed in the printing apparatus which receives image data of each raster block from the host apparatus.
FIG. 11 is a view showing an example of the relationship between the size of a printing medium, a target printing area, and the size of image data. In FIG. 11, reference numeral 111 denotes a printing medium; 112, a target printing area by the printing apparatus; and 113, image data. FIG. 11 illustrates the printing medium 111, target printing area 112, and image data 113 in overlapping manner with each other. As shown in FIG. 11, the image data 113 has a width dw in the scanning direction (x direction) and a length dh in the conveyance direction (y direction). The target printing area 112 has a width aw in the scanning direction (x direction) and a length ah in the conveyance direction (y direction). The printing medium 111 has a width pw in the scanning direction (x direction) and a length ph in the conveyance direction (y direction). These dimensions satisfy pw<aw<dw and ph<ah<dh. A comparison in area is 111<112<113. In the example shown in FIG. 11, the centers of the printing medium 111, target printing area 112, and image data 113 are adjusted.
Printing is done on the entire surface of such a printing medium, and printing without any margin is expressed as marginless printing. In addition to this case, marginless printing can also be applied to printing in which a small margin is left at the edge of a printing medium and printing in which no margin is set at only a predetermined edge of a printing medium. For example, marginless printing can also be applied to printing in which no margin is set at the left edge, right edge, and trailing edge (upstream side in the paper feed direction) of a printing medium. In performing the marginless printing, image data which falls outside the area of the printing medium 111 and is not printed on the printing medium is unnecessary, and must be rejected (removed) after reception.
When, however, image data is transferred for each block of rasters, as described above, the image data is also rejected or removed for each raster block. Hence, excess raster data remains unless ½ of the difference between a height (length in the paper feed direction) dh of image data and a height (length in the paper feed direction) ph of the printing medium is a multiple of the height of the raster block. Printing starts from a position deviated by excess rasters, and the start position of marginless printing in the paper feed direction shifts from a position intended by the user.